Support new import rules.

sdk/lib/_internal/compiler/implementation/warnings.dart

Index: sdk/lib/_internal/compiler/implementation/warnings.dart
diff --git a/sdk/lib/_internal/compiler/implementation/warnings.dart b/sdk/lib/_internal/compiler/implementation/warnings.dart
index 53f5e062c02676b4eff4c9b036bb93f713b7233e..93a1a04519898ba330aa159e9f3eae78e42aa10c 100644
--- a/sdk/lib/_internal/compiler/implementation/warnings.dart
+++ b/sdk/lib/_internal/compiler/implementation/warnings.dart
@@ -75,9 +75,15 @@ class MessageKind {
   /// Should describe how to fix the problem. Elided when using --terse option.
   final String howToFix;
 
-  /// Examples will be checked by
-  /// tests/compiler/dart2js/message_kind_test.dart.
-  final List<String> examples;
+  /**
+   *  Examples will be checked by
+   *  tests/compiler/dart2js/message_kind_test.dart.
+   *
+   *  An example is either a String containing the example source code or a Map
+   *  from filenames to source code. In the latter case, the filename for the
+   *  main library code must be 'main.dart'.
+   */
+  final List examples;
 
   const MessageKind(this.template, {this.howToFix, this.examples});
 
@@ -188,6 +194,59 @@ class MessageKind {
       error: const MessageKind('Error: Duplicate import of "#{name}".'),
       warning: const MessageKind('Warning: Duplicate import of "#{name}".'));
 
+  static const MessageKind HIDDEN_IMPORT = const MessageKind(
+      "Warning: '#{name}' from library '#{hiddenUri}' by '#{name}' "
+      "from library '#{hidingUri}'.",
+      howToFix: "Try adding 'hide #{name}' to the import of '#{hiddenUri}'.",
+      examples: const [
+          const {
+'main.dart':
+"""
+import 'dart:async'; // This imports a class Future.
+import 'future.dart';
+
+void main() {}""",
+
+'future.dart':
+"""
+library future;
+
+class Future {}"""},
+
+          const {
+'main.dart':
+"""
+import 'future.dart';
+import 'dart:async'; // This imports a class Future.
+
+void main() {}""",
+
+'future.dart':
+"""
+library future;
+
+class Future {}"""},
+
+          const {
+'main.dart':
+"""
+import 'export.dart';
+import 'dart:async'; // This imports a class Future.
+
+void main() {}""",
+
+'future.dart':
+"""
+library future;
+
+class Future {}""",
+
+'export.dart':
+"""
+library export;
+
+export 'future.dart';"""}]);
+
   static const MessageKind DUPLICATE_EXPORT = const MessageKind(
       'Error: Duplicate export of "#{name}".');